Many systems depend on the accurate and durable angular alignment of components. For example, a military training system may simulate a combat environment using optical emitters such as lasers mounted to simulated weapons, and sensors on various targets to register when laser light hits the targets, indicating accurate fire. In order to ensure effective training, it is required that the lasers “point” or accurately be boresighted in the direction an actual or simulated weapon would fire. Because of variations in the manufacture of lasers such as vertical cavity surface emitting lasers (VCSELs), adjustment of the laser alignment is often necessary to achieve accurate boresighting.
Military training is also an example of an environment in which alignments may be difficult to maintain. Lasers and other equipment may undergo intense shock and vibration, and mounting and alignment systems for the lasers should maintain proper alignment even when subjected to such treatment. Even in less demanding environments, the alignment process should be easy to accomplish and stable once achieved. For example, laboratory optical experiments may be facilitated when laser alignment is simple and reliable, reducing alignment time and minimizing production and testing costs.
Previous alignment systems have been complex, expensive, and prone to misalignment in dynamic environments. One particular prior system uses a pair of wedge-shaped prisms, called Risley prisms, placed sequentially in the path of a laser. The prisms may be rotated independently about the optical axis of the laser. Rotating the prisms with respect to each other changes the net overall deflection of the beam, and rotating the prisms as a pair changes the direction in rotation in which the deflection takes place, so that the beam may be aimed in any direction within a small solid angle about the nominal laser axis. Such a system has several moving parts, including the prisms and elements for actuating the prisms. The prisms introduce four optical surfaces into the optical path, which result in loss of signal in the system, as well as produce stray reflections. The surfaces of the prisms may become dirty, cloud up due to condensation, or otherwise lose transparency due to environmental effects. Shock and vibration control is harder to achieve when multiple parts are included in an assembly. Misalignment and breakdown will often occur.
There is accordingly a need for an angular alignment device that is mechanically simple and reliable, and alleviates the above problems.